Resonance-frequency variable resonator

ABSTRACT

A resonance frequency variable resonator is provided, which comprises a ferrite strip line having a ferrite chip, and a varactor diode electrically connected to the ferrite strip line. Each of the reactances of the ferrite strip line and the varactor diode is controlled by a magnetic field and a bias voltage applied thereto so as to establish the resonance frequency of the resonator as desired. Since the ferrite strip line and the varactor diode complement each other, the resonator has many excellent properties, high speed responsiveness, wide variation range, reliability, and so on.

United States Patent [191 Anbe et al.

[ Oct. 16, 1973 RESONANCE-FREQUENCY VARIABLE RESONATOR [75] Inventors:Toshi Anbe; Yukimichi Tokuzawa, Kadoma, Japan Company, Kadoma City,Osaka, Japan May 19, 1971 211 App]. No.: 144,886

[30] Foreign Application Priority Data May 21, 1970 Japan 45/44236 [52]US. Cl 331/99, 330/21, 330/31, 331/117 D, 331/177 V, 333/82 B, 334/4,334/15 [51] Int. Cl. H03b 5/18 [58] Field of Search 330/21, 31; 331/96,331/99, 177 V, 117 D; 333/24.2, 73 S, 82 B,

OTHER PUBLICATIONS L. Lewin, A Resonance Absorption lsolator InMicrostrip For 4 GC/S, The IEE, Part B Supplement, Convention onFerrites, Oct.-Nov. 1956 Primary Examiner-Paul L. Gensler Attorney-JohnLezdey [57] ABSTRACT A resonance frequency variable resonator isprovided, which comprises a ferrite strip line having a ferrite chip,and a varactor diode electrically connected to the ferrite strip line.Each of the reactances of the ferrite strip line and the varactor diodeis controlled by a magnetic field and a bias voltage applied thereto soas to establish the resonance frequency of the resonator as desired.Since the ferrite strip line and the varactor diode complement eachother, the resonator has many excellent properties, high speedresponsiveness, wide variation range, reliability, and so on.

8 Claims, 4 Drawing Figures llj FERRITE I6 I 1 K 13 VARACTOR DIODEPATENTED BUT I 8 I975 SHEET 2 BF 2 H/SL INVENTOR TOR u 705! ANBE 4YuKlmlcHl AU A I 1/! RESONANCE-FREQUENCY VARIABLE RESONATOR Thisinvention relates to a resonator and more particularly relates to aresonance-frequency variable resonator including solid variablereactance devices.

Various resonance-frequency variable resonators are known in the art,one of which is a resonator using a variable capacitor havingmechanically movable pairs of electrodes. This type of capacitor ispresently considered rather obsolete and is practically unusable forautomatically controlled resonators. Another type of resonator is theone using a varactor diode having a variable capacitance formed in adepletion layer thereof. This resonator is advantageous for its highspeed responsiveness, controllability, and so on. A problem is stillencountered in incorporating a plurality of resonators of this type in asingle system such as a super-heterodyne radio receiver and amulti-stage tuned amplifier, because it is difficult to have availablethose varactor diodes which possess capacitance variationcharacteristics coinciding. with one another.

It is therefore an object of this invention to provide an improvedresonance-frequency variable resonator including a varactor diode and aferrite strip line element which is free from such drawback asabovementioned.

Another object of this invention is to provide a resonator theresonance-frequency of which is varied by two parameters.

Further object of this invention is to provide a resonator having a wideresonance-frequency variation range.

Still further-object of this invention is to provide aresonator havingan easily controllable reactance.

Further object of this invention is to provide a resonance-frequencyvariable resonator with high reliability and stability.

Still further object of this invention is to provide aresonance-frequency variable resonator usable for UHF range.

Further object of this invention is to provide a resonance-frequencyvariable resonator which can be readily rendered to a solid state.

Still further object of this invention is to provide aresonance-frequency variable resonator useful for a local oscillator ofa super-heterodyne receiver.

Further object of this invention is to provide a resonance-frequencyvariable resonator useful for a multistage tuned amplifier.

In the drawings:

FIG. 1 is a perspective view of a resonator according to this invention;

FIG. 2 is a diagram showing the resonator of FIG. 1; I

FIG. 3 is a diagram showing an oscillator using a modification of theresonator of this invention; and

FIG. 4 is a diagram showing a two-stage tuned amplifier using anothermodification of the resonator.

The resonator of this invention includes a ferrite strip line elementand a varactor diode which complement each other.

A preferred embodiment of the resonator of this nature, generallyindicated by 11 in FIG. 1, comprises aferrite strip line element SLincluding astrip line structure constituted by a pair of outerconductors l2 and 12' and an inner conductor 13 positioned between andan equivalent circuit of spaced apart from the conductors 12 and 12',and a pair of ferrite plates 14 and 14' interposed as insulators betweenthe inner conductor 13 and the outer conductors 12 and 12. Although theferrite plates 14 and 14' are herein shown as spaced apart,- they maypreferably be in contact with each other with the inner conductor 13sandwiched therebetween. The outer conductors 12 and 12' areelectrically connected to each other so as to have a common electricalpotential. If desired, either of the outer conductors 12 and 12' may beremoved to provide ease of production which will be more or less offsetby a degraded performance efficiency. An end of the inner conductor 13is connected through a line 16 and a capacitor 17 to a cathode terminalof a varactor diode VD. This varactor diode has an anode terminalconnected through a line 16' to that portion of the conductor 12 or 12which is nearest the above-mentioned end of the inner conductor 13. Avariable voltage d.c. power source 18 has positive and negativeterminals which are connected to the anode and cathode terminals of thevaractor diode VD, respectively. The lines 16 and 16' are also connectedto input terminals 19 and 19 through which an a.c. signal from an a.c.signal source 21 are applied. The varactor diode VD is reversely biasedby the d.c. power source 18 and the capacitance C of the varactor diodeVD is varied in proportion to the variation of the d.c. voltage fromsource 18. On the other hand, a magnetic field H is applied to theferrite strip line SL as indicated by an arrow H. This magnetic field isproduced by a solenoid 22 having a core energized by a variable voltaged.c. power source 23. An effective permeability of each of the ferriteplates 14 and 14' is varied in accordance with the variation of anintensity of the magnetic field H. The intensity of the magnetic field Hlies within a magneticresonance region of 1,000 to 3,000 gauss forinstance in order to attain a steep variation of the effectivepermeability in terms of the variation of the magnetic field. A ferritematerial making up the ferrite plates should have as high rate aspossible ofchange of effective permeability within themagnetic-resonance region. In this embodiment, the outer conductors 12and 12' are connected direct to the inner conductor 13 at their endsopposite to the lines 16 and 16. A modified configuration may be putinto practice for separating the reverse biasing voltage source and thestrip line structure of the strip line element SL from each other. Forexample, the

A variable capacitor 24 having a capacitance C corresponds to thevaractor diode VD, and a'pair of lines 25 and 25 of the length Irepresent the ferrite strip line elements SL. The characteristicimpedance Z0 of the lines 25 and 25' is given by VII/E; where p. and e,respectively represent the effective permeability and the dielectricconstant of the ferrite plates 14 and 14'.

Here, since the resistance and conductance of the ferrite strip lineelement SL are so small as to be negligible, the reactance of theferrite strip line element SL is given by Zo'tanfll. Hence, anangularvelocity to of a v resonance frequency of the resonator 11 is defined byw-C'Zo'tanBl 1 where B =10 m From above equation (1), it is apparentthat the variation of the resonance frequency of the resonator 11 ofFIG. 1 is effected by varying either the magnetic field H or the biasvoltage of the source 18. If an ac. signal having a wavelength A therange of which is defined by M8 2 l is applied to the resonator 11, thefollowing equation will hold.

Then, the equation (1) can be translated into 'C'pxl l Hence, wa t (3 orw a C (4) From above expressions (3) and (4), it is evident that boththe capacitance C and the permeability p. define the resonance frequencyof the resonator 11 substantially independently of each other, as far asthe wavelength )r is localized in a region defined by M8 2 I.

In this instance, it should be noted that, since the angular velocity orshould be real, tanBl is larger than 0. The length l is thus expressedas where n 0, l, 2,

Although the inner and outer conductor herein shown as electricallyconnected at one end thereof to each other in the present embodiment, aferrite strip line element which is modified to have its inner and outerconductors isolated from each other may be used by preference. In thiscase, the characteristic reactance is given by Zo'cotBI, and theequation (1) can be replaced by Similarly, the length l is given by(2n+l) M4 l (n+l) ./2

where n 0, l, 2,

Comparison between the expressions (5) and (5) will suggest that theformer ferrite strip line element having short-circuited outer and innerconductors is advantageous over the latter for its compactness.

Referring to FIG. 3, a modified form of the resonator of this inventionis shown as employed for a local oscillator 31 cooperating with afrequency converter of a superheterodyne radio receiver. This oscillatorincludes a transistor TR having a base connected through a resistor R,to a negative bus line 32 which is connected through a feed-throughcapacitor C, to a negative terminal of a d.c. power source (not shown).The base of this transistor is grounded through a resistor R by-passedby a capacitor C The transistor TR has its emitter connected through aresistor R to the negative bus line 32 and its collector connected toone end of an inner conductor of a strip line element SL the other endof which is connected direct to outer conductors and is also grounded. Asuitable magnetic field H is applied to the strip line element SI... Thecollector is also connected to a trimmer capacitor or adjustablecapacitor C, which is in turn connected to an anode terminal of avaractor diode VD shunted by a trimmer capacitor C.,. A cathode terminalof the varactor diode VD is grounded.

To the anode terminal of the varactor diode VD is applied an AFC(automatic frequency control) voltage from an after-stage such as anintermediate frequency amplifier through a resistor R.,. In a normalcondition, the AFC voltage is fixed at a predetermined level and theoscillator 31 oscillates at a resonance frequency of the resonator 11defined by the given magnetic field and the AFC voltage. In thisinstance, it should be noted that a frequency of a signal from abroadcasting station is liable to deviate from the central frequencythereby to affect the performance quality of the radio receiver. The AFCvoltage is adapted to deviate from the predetermined level in proportionto the deviation of the frequency of the received signal through such asan antenna. Therefore, the capacitance of the varactor diode VD isvaried in proportion to the deviation of the frequency of the receivedsignal. As a result, the resonance frequency of the resonator 11, thatis, the oscillation frequency of the oscillator 31, is adjusted. Thisadjustment is quickly accomplished by the high speed responsiveness ofthe varactor diode VD even when the frequency of the received signaldeviates at a high speed.

It is noteworthy that the local oscillator 31 is capable of providing awide frequency range since the variable range of the reactance of theferrite strip line can be established to be wider than that of thevaractor diode. In addition, the effective permeability p. of theferrite chip is easily controlled during production so that it is easyto obtain those ferrite chips which have a common permeability and whichare convenient for the tracking operation between the local oscillatorand a tuner (not shown). It should be now understood that the transistorTR may be replaced by another active element such as a vacuum tube.

Another modified form of the resonator according to this invention isshown in FIG. 4 as combined with a twostage tuned amplifier includingtransistors TR, and TR,. An input line 41 such as an inner conductor ofa coaxial line is provided, which is connected to an intermediate pointof inner conductor 13 of a strip line SL,. The inner conductor 13 isgrounded at one terminal and connected at the other to a cathodeterminal of a varactor diode VD, and through a coupling capacitor C toan emitter of the transistor TR,. This emitter is connected to anegative d.c. source through a resistor R,, and a feed-through capacitorC,,-,. A bias potential at a base B, of the transistor TR, isestablished by a resistor R and a resistor R one terminal of which isgrounded. The other terminal of the resistor R is connected to the baseB, of the transistor TR, and one terminal of the resistor R which isconnected at the other terminal to the negative source. A by-passcapacitor C is connected to the base B, which is grounded so as to passa signal component therethrough. A collector C, of the transistor TR, isconnected to one end of an inner conductor 13' of a second strip lineelement 81.: of a second stage.

Adjustable capacitors C and C are provided in order to supplement thevaractor diode VD One terminal of the capacitor C is connected to theanode of the varactor diode VD, and the other terminal is grounded. Oneterminal of the capacitor C is connected to the cathode of the varactordiode and the other terminal is grounded.

One terminal of the inner conductor 13' is grounded and the other end isconnected to a second varactor VD To a suitable intermediate point ofthe inner conductor 13' is connected an emitter E of the transistor TRthrough a coupling capacitor C The emitter E is connected through aresistor R and a feed-through capacitor C to a negative bias d.c.source. A potential of a base B of the transistor TR is established byresistors R and R One terminal of the resistor R is connected to thenegative bias source through the feedthrough capacitor C and the otherterminal is connected to the base B and to one terminal of the resistorR the other terminal of which is grounded. A by-pass capacitor C isconnected to the base B which is grounded so as to pass a signalcomponent therethrough. A collector C of the transistor TR; is connectedto a succeeding stage (not shown). Adjustable capacitors C and C areprovided in order to supplement the varactor diode VD One terminal ofthe capacitor C is connected to an anode of the varactor diode VD andthe other terminal is grounded. One terminal of the capacitor C isconnected to the cathode terminal of the varactor diode VD and the otherterminal of the capacitor C is grounded. A stepwise varied negative d.c.voltage is applied to the respective anode terminals of the varactordiodes VD, and VD through a terminal S, a resistor R and inductors L andL to bias the varactors VD, and VD The ferrite strip line elements SL,and SL are on the other hand, subject to a common magnetic field H.

When in operation, a plurality of high frequency signals are appliedthrough the input line 41 to the strip line SL,. The input signalshaving the same frequency as the resonance frequency of the resonator111 constituted by the strip line SL, and the varactor diode VD areselectively transmitted one by one to the one end 13a. This signal isapplied through the coupling capacitor to the emitter E, and thenamplified by the transistor TR, The amplified signal is applied to theone end 13a of the strip line 13'. After filtered by the resonator 211constituted by the strip line SL and the varactor diode VD the signal isapplied through the coupling capacitor C to the emitter E and thenamplified by the transistor TR The thus amplified signal is transmittedto the succeeding stage through the collector C On the other hand, themagnetic field H which is applied to the strip line elements 'SL, and SLand the voltage through the terminal S is regulated, respectively, so asto establish the respective resonance frequencies of the resonators 111and 211. The transistors TRl and TR2 may be replaced by other activeelements such as vacuum tubes.

This amplifier finds especially advantageous applications in a receiverfor wireless communication to selectively receive one of carrier wavescorresponding to a channel localized within a certain band. In suchcase, the magnetic field H is firstly adjusted to select a band withinwhich a plurality of carrier channels are localized. The voltage throughthe terminal S is secondly selected to select one of the carrier waveslocalized within the band firstly selected. If further regulation of theresonance frequency is required, the magnetic field H may be regulated.

It is now appeared that, since the resonator of this invention dispenseswith mechanical moving elements and is constructed in a simple manner,it not only offers a high reliability but is ready for commercialproduction.

What is claimed is:

1. A resonance-frequency variable resonator comprising: a ferrite stripline element including an inner conductive plate, at least one outerconductive plate facing said inner conductive plate, and at least oneferrite plate positioned between said inner and outer conductive platessaid ferrite line element being subjected to a magnetic field; avaractor diode having anode and cathode terminals which are connected tosaid inner and outer conductive plate; and biasing source means forapplying a reverse bias to said varactor diode.

2. A resonator according to claim 1, wherein said anode and cathodeterminals are respectively connected to ends of said inner and outerconductive plates through at least one capacitor, and said inner andouter conductive plates are connected to each other at the opposite endsthereof.

3. A resonator according to claim 1, wherein said magnetic field isvaried within a region of magnetic resonance of said ferrite plate.

4. A resonator according to claim 1, comprising a pair of outerconductive plates which are connected to each other for having a commonelectric potential.

5. A resonator according to claim 1, further comprising a supplementalcapacitor parallel with said varactor diode.

6. A resonance-frequency variable resonator, in combination with anoscillator including an active element, which resonator comprises aferrite strip line element including an inner conductive plate which isgrounded at one end and adapted to be connected at the opposite end tosaid active element, at least one outer conductive plate which isgrounded at both ends, and at least one ferrite plate positioned betweensaid inner and outer conductive plates and subjected to a variablemagnetic field; a varactor diode having an anode which is connectedthrough a capacitor to said opposite end of said inner conductive plateand to a negative variable voltage source, and a cathode terminal whichis grounded.

7. A resonator according to claim 6, wherein said varactor diode isshunted by a supplemental capacitor.

8. A resonance-frequency variable resonator in combination with a tunedamplifier including at least one active element, which resonatorcomprises a ferrite strip line element including an inner conductiveplate which is grounded at one end and adapted to be connected at theopposite end to said active element through a coupling capacitor, theintermediate portion of said inner conductive plate being connected toan input line, at least one outer conductive plate grounded at bothends, and at least one ferrite plate positioned between said outer andinner conductive plates and subjected to a variable magnetic field; anda varactor diode having a cathode which is connected to said oppositeend of said inner conductive plate and an anode which is connected to anegative variable d.c. voltage source.

1. A resonance-frequency variable resonator comprising: a ferrite stripline element including an inner conductive plate, at least one outerconductive plate facing said inner conductive plate, and at least oneferrite plate positioned between said inner and outer conductive platessaid ferrite line element being subjected to a magnetic field; avaractor diode having anode and cathode terminals which are connected tosaid inner and outer conductive plate; and biasing source means forapplying a reverse bias to said Varactor diode.
 2. A resonator accordingto claim 1, wherein said anode and cathode terminals are respectivelyconnected to ends of said inner and outer conductive plates through atleast one capacitor, and said inner and outer conductive plates areconnected to each other at the opposite ends thereof.
 3. A resonatoraccording to claim 1, wherein said magnetic field is varied within aregion of magnetic resonance of said ferrite plate.
 4. A resonatoraccording to claim 1, comprising a pair of outer conductive plates whichare connected to each other for having a common electric potential.
 5. Aresonator according to claim 1, further comprising a supplementalcapacitor parallel with said varactor diode.
 6. A resonance-frequencyvariable resonator, in combination with an oscillator including anactive element, which resonator comprises a ferrite strip line elementincluding an inner conductive plate which is grounded at one end andadapted to be connected at the opposite end to said active element, atleast one outer conductive plate which is grounded at both ends, and atleast one ferrite plate positioned between said inner and outerconductive plates and subjected to a variable magnetic field; a varactordiode having an anode which is connected through a capacitor to saidopposite end of said inner conductive plate and to a negative variablevoltage source, and a cathode terminal which is grounded.
 7. A resonatoraccording to claim 6, wherein said varactor diode is shunted by asupplemental capacitor.
 8. A resonance-frequency variable resonator incombination with a tuned amplifier including at least one activeelement, which resonator comprises a ferrite strip line elementincluding an inner conductive plate which is grounded at one end andadapted to be connected at the opposite end to said active elementthrough a coupling capacitor, the intermediate portion of said innerconductive plate being connected to an input line, at least one outerconductive plate grounded at both ends, and at least one ferrite platepositioned between said outer and inner conductive plates and subjectedto a variable magnetic field; and a varactor diode having a cathodewhich is connected to said opposite end of said inner conductive plateand an anode which is connected to a negative variable d.c. voltagesource.